Okay, my M3 is running low on oil and it demands a quart of oil. i don't have that castro oil, but i do have Mobil 1 Synthetic Motor oil 5W-30. will this work? or would i have to use the recommend castro oil???

i do have Mobil 1 Synthetic Motor oil 5W-30. will this work? or would i have to use the recommend castro oil???

I wouldn't do it.
You should spring for the hard to find, expensive, recommended, 10w-60. I don't think the brand is as important as the weight.
Keep in mind the thing holds about 9 quarts. In my case, after a 1 quart low warning on the dash, I put in about 1/2 quart and the indicator went to the full mark. As someone pointed out, add a little and see were the mark is. If you just put in the whole quart, you could trigger an overfill warning.

I wouldn't do it.
You should spring for the hard to find, expensive, recommended, 10w-60. I don't think the brand is as important as the weight.
Keep in mind the thing holds about 9 quarts. In my case, after a 1 quart low warning on the dash, I put in about 1/2 quart and the indicator went to the full mark. As someone pointed out, add a little and see were the mark is. If you just put in the whole quart, you could trigger an overfill warning.

Of course if given a choice, he should use the Castrol TWS.

but if he's in a bind and needs oil, Mobile 1 is sufficient. He's adding 1/4 to 1/2 L of synthetic oil into an engine 8L+ oil capacity, which is no big deal. You'll rather have oil than not have oil. That's why the owners manual say, that Mobile 1 or the likes (synthetic with similar viscocity levels) are okay when you're in a bind and can't find TWS.

Pg 208 Alternate oil types...personally I wouldn't sweat it though. I'd just take it home & top it off tomorrow.

This is contrary to the manual and common bad advice on here for the past 5 years. You should in at least 1/2qt increments because the stupid e-dipstick could get confused with smaller amounts. Also adding too much oil can cause engine damage as well. That's why I always wait till it says to add 1+ and I will add 1/2 then check level before I add another 1/2.

I won't run that 10W-60 sludge BMW touts. I got the low oil warning 600 miles from home and will wait til I get back to add some Redline 5W-30. Keep in mind that this is an 8+ quart motor. Being down a quart or even two won't hurt one bit on the street.